"The problem with this idea is context or the need for metadata. Keeping track of your network in each group is simple, but each network has a different purpose and that purpose could be different based on the person creating the network. For example, I use Facebook mainly for personal contacts, but other people use it for business. I use LinkedIn for business, and Twitter is a mix of business and personal. Each contact in each network has specific context (or metadata) that makes that connection mean something. For people, that context is implicit but for an application the context needs to be built and managed explicitly. I would love to have something like this as well, but with the number of network-enabled services, even the development becomes difficult. Also, how does this fit with the idea of a single digital identity that is shared across all of these services?" - Rob Diana